From the Division of Health Administration and Promotion, Department of Social Medicine, Faculty of Medicine, Tottori University (Dr Kurozawa, Dr Hosoda, Dr Nose) and Center of Vibration Syndrome San-in Rosai Hospital, Yonago, Japan (Dr Nasu).
Address correspondence to: Youichi Kurozawa, MD, Division of Health Administration and Promotion, Department of Social Medicine, Faculty of Medicine, Tottori University, Yonago 683-8503 Japan; e-mail: email@example.com.
Copyright © by American College of Occupational and Environmental Medicine
The prognosis of vibration-induced white finger was investigated with a long follow-up period. From 1975 to 1994, 99 men with hand-arm vibration syndrome who received the annual compulsory examination at San-in Rosai Hospital were followed up for 15 years or longer. Based on the extent of finger-blanching attacks described in the medical records, they were classified according to the vascular stage of the Stockholm workshop scale. In our laboratory, finger systolic blood pressure (FSBP) measurement after finger cooling has been performed since 1989. We compared the stage classification with the results of FSBP measurement after finger cooling in the period 1989–1994. The stage 2 and stage 3 groups showed a significant decrease in FSBP% compared with the stage 0 group. The vascular stage classification based on subjective symptoms in this study was to a certain extent reliable. Although vibration-induced white finger symptoms tended to improve to some extent, 43.2% and 70.4% of patients with stage 2 and stage 3 at first examination, respectively, still suffered from finger blanching attacks after 15 years of observation. Blanching of fingers in advanced stages, especially stage 3, was found to be persistent many years after cessation of vibration exposure.
The intermittent blanching of the fingers is the most prominent symptom resulting from occupational exposure to vibration. It is called vibration-induced white finger (VWF). Many follow-up studies 1–10 of VWF subjects have been performed, and most of them have indicated that VWF can improve when exposure to vibration is reduced or ceased. The follow-up periods in these studies, however, were not very long. Therefore, the prognosis for VWF subjects has not been fully clarified. To investigate the prognosis of VWF subjects over a long follow-up period, we analyzed data from medical records on patients with VWF at San-in Rosai Hospital, Japan. Staging of VWF based on subjective symptoms was undertaken according to the Stockholm workshop scale. We investigated the time-dependent changes of the vascular stage in each of the patients. In our laboratory, finger systolic blood pressure (FSBP) measurement after finger cooling as an objective test of VWF has been performed since 1989. We compared the vascular stage classification with the results of FSBP measurement after cooling.
Subjects and Methods
From 1975 to 1980, 113 men with hand-arm vibration syndrome (HAVS) received their first examination at San-in Rosai Hospital. Fourteen (12.4%) of them dropped out of this study during the 1980 second examination, leaving a total of 99. All the subjects were officially recognized as having HAVS by the Japanese Ministry of Health, Labor and Welfare. Ninety-nine (87.6%) patients were followed-up for 15 years and longer, from 1975 to 1994. They consisted of 87 chain-saw operators, 4 rock drillers, and miscellaneous others. Sixty-one of them had discontinued vibration exposure at the first examination and the others had stopped using vibrating tools within a few years.
It was realized that the vascular stage of the Stockholm workshop scale 11 permits reliable grading of severity using all symptoms. Palmer and Coggon 12 concluded that expressions such as “occasional attacks,” “frequent attacks, ” and “most fingers” described in the scale need to be defined before cases can be unambiguously classified. Furthermore, the frequency of attacks depends on various factors under the control of the subject, eg, use of protective clothing and avoidance of cold exposure. Hence, the extent of blanching is considered to be a more reliable and desirable index of severity in epidemiological studies. In this study, the subjects were classified according to the vascular stage of the Stockholm workshop scale based on the extent of finger blanching attacks described in the medical records. The vascular stage for each of the subjects was determined every year during the follow-up period. Information from the medical records included smoking habits, other diseases, occupation, vibratory tools, periods of exposure to vibration, and the results of laboratory tests. Patients with finger blanching attacks had been treated primarily with a peripheral vasodilator (calcium channel antagonist) during the follow-up period. Table 1 shows the characteristics of the study population at the first examination.
In our laboratory, FSBP after finger cooling using strain-gauge plethysmography (Digimatic 2000, Medimatic, Copenhagen) has been performed since 1989. 13 The subjects were asked to abstain from smoking, alcohol, and food intake for at least 2 hours before the examination. The examinations were conducted in a room with temperature and humidity controlled at 26°C and 50%, respectively. They were lightly dressed and rested for at least 30 minutes in the room before the examination. An occluding cuff and a double-inlet cuff were placed on the proximal and middle phalanxes respectively of the most affected finger. Only an occluding cuff was placed on the proximal phalanx of the thumb as a reference finger. In the subjects without finger blanching symptoms, the middle finger and the thumb were used. Strain-gauges were placed on each distal phalanx. A laser-Doppler probe was attached with a double-sided adhesive tape to the center of the volar side of the distal phalanx of the affected finger. Digital blood circulation was stopped with suprasystolic pressure by the occluding cuff. FSBP was measured by slowly deflating the occlusion cuff and recording the first increase in fingertip volume with the strain-gauge or the first increase in digital skin blood flow with the laser-Doppler technique. The test was repeated after finger cooling at 10°C for 5 minutes. Finger cooling was performed using the double-inlet cuff at 10°C for 5 minutes. The change in FSBP on cooling at 10°C was expressed as the percentage of FSBP (FSBP%) according to the formula from Nielsen and Lassen 14
Table 2 shows time-dependent changes of the vascular stage in 99 men with HAVS. Five (15.2%) of 33 men with stage 0 initially became stage 2 at 15 years following the first examination. Both patients with stage 1 initially had no blanching attacks 15 years after the first examination. Thirteen (35.1%) of 37 patients with stage 2 had improved to stage 0, and 1 (12.7%) had deteriorated to stage 3 five years after the first examination. At 10 years, 18 (48.6%) had changed to stage 0, and 5 (13.5%) had deteriorated to stage 3. At 15 years, 24 (64.9%) of the patients with stage 2 at the first examination had improved, with 21 patients (56.8%) recovering to stage 0, but 5 (13.5%) had deteriorated to stage 3. Two (7.4%) and 6 (22.2%) of 27 patients with stage 3 at first examination had improved to stage 0 after 5 years and 10 years respectively. Eight (29.6%) of 27 patients with stage 3 at the first examination had changed to stage 0 and 19 (70.4%) had been improved after 15 years of observation.
Figure 1 shows the results of FSBP% in the different stage groups based on subjective symptoms in 1989 to 1994. The stage 2 and stage 3 groups showed a significant decrease in FSBP% compared with the stage 0 group. There was, however, no significant difference in FSBP% between the stage 2 and stage 3 groups.
The subjects in our study had moderate to severe (stage 2 and stage 3) VWF and were officially recognized as HAVS by the Japanese Ministry of Health, Labor and Welfare. Fourteen patients dropped out. Their conditions (age, symptoms, smoking habits, occupation, vibratory tools, periods of exposure to vibration) at first examination did not differ significantly from those of subjects included in the study. Patients with VWF generally tend to avoid cold exposure. It was noticed that the frequency of blanching attacks was reduced in most of the patient with VWF after the first examination. If we had relied on frequency of attacks during the follow up period, we could have underestimated severity. So we used the extent of finger blanching attacks rather than frequency in this study, as stated earlier.
FSBP measurement after cooling has been considered to be one of the most accurate laboratory tests for an objective confirmation of VWF. 4–6 Furthermore, Kurozawa et al 13 reported that measurements of FSBP after finger cooling was useful for assessing the severity of VWF based on frequency of blanching attacks. In this study no significant difference in FSBP% between stage 2 and stage 3 was apparent. This may be due to staging based mainly on the extent of finger blanching attacks rather than frequency. Another possible explanation is inaccuracy of subjective symptoms that subjects reported. However, the stage 2 and stage 3 groups showed a significant decrease in FSBP% compared with the stage 0 group. It seemed that the vascular stage classification based on subjective symptoms of extent of blanching in our study was to a certain extent reliable.
Forty-three (67.2%) of the 64 patients with stage 2 and stage 3 had been improved after 15 years of observation, although a few cases had deteriorated. VWF tended to improve to some extent after cessation of vibration exposure. However, 70.4% of the patients with stage 3 at the initial examination and 43.2% with stage 2 at the initial examination were still suffered from finger blanching attacks after 15 years of observation. Ogasawara et al 10 reported that during a 6-year follow-up period improvement of VWF was observed in 46% of patients in stage 1 initially, but in only 17% of those in stage 3 initially. They found that severe stage 3 VWF tended to be more persistent.
The results of our study indicated an adverse prognosis for those subjects in the more advanced stages of VWF. Our findings also indicated that blanching of fingers in advanced stages, especially stage 3, was persistent many years after a cessation of vibration exposure in spite of medical treatments. Severe VWF seems to be irreversible. However, it is important to prevent the progression of VWF as well as the onset of VWF. Detection of circulatory disturbance, avoidance of further HAV exposure, and commencement of treatment in the early stage of VWF, have been found to be beneficial.
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